Synthetic Populations – Sources of Precocity in Maize Breeding

Research Journal of Agricultural Science, 44 (2), 2012

SYNTHETIC POPULATIONS – SOURCES OF PRECOCITY IN MAIZE BREEDING

I. HAS1,2, Voichiţa HAS2, A. GULEA3

1University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca 3-5 Mănăştur Street, Postcode 400372, Cluj-Napoca, Romania 2 Agricultural Research and Development Station Turda 3Cattle Research and Development Station, Targu-Mures, Romania E-mail: [email protected]

Abstract: In the maize breeding the local landraces precocity, such as: Avram Iancu, Bereni, Corbu could presented a special interest, evenly like 189-84, Cerbal, Dumbravita, Desesti, Mara1, useful gene sources for adapting capacity and for Mara2, Eremitu, Giulesti, Satu Lung, Satu Mare, physiological and agronomical traits and for Tarna Mare, Vlaha, and synthetic populations Tu valuable quality. The exploration of these Syn. 6, Tu Syn Mara1, Tu Syn Gutin, Tu SRR resources can be possible only through complexes 2I(5D), Myn Syn AS-G. The determination of the studies and measures which will determine the genetic value of seven synthetic consisted in their biodiversity keeping and the sustainable use of this. crossing with four testers (inbred lines): two flint The creation of maize hybrids which, among other inbred lines (TD 233 and CO 255) and two dent features, to be early it is a big concern of breeder inbred lines (TC 184 and TC 209). The test crosses teams. In northern and pre-montane areas, due to and their parental forms were evaluated in four thermal lowered resources, precocity is environmental conditions: two years 2009 and indispensable to achieving maturity. The objectives 2010 and two locations Turda and Targu-Mures of this research were: -to explore the phenotypic respectively, for both per se and test cross variability existing for early maturity in a large performances. The highest values of additive effects range of maize local and synthetic populations; -to for grain dry matter content were recorded at: Tu identify genotypes that could be interesting in Syn Mara (ĝn = +1.80), Tu SRR 5D (2I) (1) (ĝn = heritability of short growing season. It was noticed +0.62) and Tu Syn 1 (ĝn = +0.45). Therefore, Tu some maize local populations which can be used Syn Mara, Tu SRR 5D (2I)(1) and Tu Syn 1 like initial genetic material for breeding of produced hybrids with the most early maturity.

Key words: maize germplasm, precocity, GCA, general combining ability; SCA, specific combining ability

INTRODUCION The maturity ratings of maize (Zea mays L.) varieties usually grown in Transilvania (central and north-western Romania) rang from FAO 100 to 400. Late material normally shows too much moisture at normal harvesting time and then presents problems with storage. This severely limits the scope of the germplasm that can be used in a breeding program located in this area. Selection for early flowering and low moisture at harvest adapts later material to areas that require earlier maize (GIESBRECHT, 1960; ORDAS, 1988; HAWBAKER et al., 1996; GONZALEZ et al., 1997; TROYER, 2001; TALLER and BERNARDO, 2004; SHRANG et al., 2006) Choosing reliable maize varieties that are early maturing is essential for maize growers in the areas with limited heat treatment, but that doesn’t mean losing out on yield. These genotypes, in effect, require a shorter growing season than later maturing ones. Flint x dent maize hybrids are commonly planted in the early corn growing regions of Europe (northern and the Atlantic Coast of Europe). Evaluation of the early maize germplasm is important for the development of new commercial hybrids adapted to cooler summer regions (REVILLA et al., 1999; GONZALEZ et al., 2000). Local populations to improve maize may be of particular interest, especially as gene 33 Research Journal of Agricultural Science, 44 (2), 2012 sources for resilience and some agronomic properties (MURARIU et al., 2010). The most valuable populations have undergone extensive works of inbreding and selection for the creation of inbred lines, hybrids that provide it with a better language capacity to adapt in comparison with foreign hybrids. Partial results confirmed expectations (SARCA, 2004). Local populations of maize are distinguished by a great capacity of adaptability and physiological properties specific to certain areas, and a production capacity and outstanding quality. Each population bears the imprint of the environment in which it was formed (TROYER, 2001). Romanian local populations are very different, as are the environmental conditions in our country. Local populations are the result of a long process of evolution, under the action of factors that determine evolution, possessing assets particularly valuable that the inbred lines can transfer these traits of hybrids, which highlight the poignancy of appropriating adaptability (CRISTEA, 1978). Development of such hybrids is fully possible, whereas in local populations of corn in our country there are genetic factors responsible for the manifestation of these assets. For efficient use of local germoplasm, it must be inventoried and stored valuable genes. Characterizing maize genetic resources and understanding the structure of the diversity they encompass should lead to enhanced utilization for the improvement of this crop. Vegetative traits can be included as descriptors for describing and characterizing maize germplasm (ORTIZ et al., 2008; ORTIZ et al., 2009). The obtaining of maize hybrids which, among other features, to be early too, represents an important concern of the maize breeders. Early maize must grow faster and mature sooner under cooler conditions than later maize, to produce mature kernel in a shorter season. Early maize grows faster, particularly in the spring when the weather is cool. European northern flint varieties, as sources of early germplasm, grow extremely fast in seedling and in juvenile plant stages, flowers sooner and reaches physiological maturity sooner than later maize (HAS, 2001). Maturity zones are based on accumulated GDUs during the frost-free period: GDU = [Max temp (≤ 300C) + Min temp (≥ 100C)]/2 - 100C. In northern and premontane areas, due to limited thermal resources, precocity is indispensable to achieving maturity (CRISTEA et al., 1986, 1986a; CABULEA, 1987). In southern areas, precocity is used to mitigate the moisture stress of late drought by sowing earlier and early use of earlier hybrids (CIOCAZANU et al., 1998; BAGIU, 1999). Some of sources of early germplasm might be local and synthetic populations breeding by recurrent selection (CRISTEA et al, 1978; GULEA, 2011; HAS et al., 2011). The inheritance of maturity in maize is governed quantitatively. In general, the genes act in an additive manner, as if many genes with small and equal effects were involved; heterosis affects flowering time about 10% (TROYER, 1994, 2001). Knowledge about germplasm diversity and genetic relationships among breeding materials could be an invaluable aid in maize improvement strategies, maize germplasm could be easily managed, using recurrent selection method (LAVERGE et al., 1991; MOHAMMADI and PRASANNA, 2003; TALLER and BERNARDO, 2004). Turda - Romania maize genotypes have great phenotypic and genetic variability, consisting of local populations, varieties, synthetics. Genotype germplasm sources range from very early to lateand from dent to flint grain characteristics (HAS et al., 2006). The objectives of this research were: -to explore the phenotypic variability existing for early maturity in a large range of maize local and synthetic populations; -to identify genotypes that could be interesting in heritability of short growing season.

34 Research Journal of Agricultural Science, 44 (2), 2012 MATERIALS AND METHODS Maize samples I. Phenotypic variability Maize samples used in this study consisted of 264 accessions from “TURDA” germplasm collection, among which there were 208 local populations (landraces), collected in different Romanian regions (Transylvania and Moldavia); 56 synthetics/composites among which 30 synthetics created at ARDS Turda and 26 synthetics acquired from different countries (Spain, Italy, Germany, University of Minnesota, University of Pennsylvania). All local populations (landraces) and synthetics are currently used in the framework of breeding and genetic program at the Agricultural Research Station, Turda – Romania (ARS Turda). The studied genotypes differed by germplasm source, grain type, maturity classification (very early, early, intermediate and late) and grain appearance and colour. Experimental designs. These genotypes were grown at the Agricultural Research and Development Station Turda – Romania (Transylvania region), in 2009. Each group of genotypes was grown in separate but adjacent trials. Experimental plots were 2-rows, 5 m - long, with 0.7 m spacing between two rows without replications. Plant densities averaged 60 000 plants/hectare in each trial. I.Statistical analysis of per se variability. All stages of growing season were performed in duplicate, and the mean value was analyzed statistically. Analyses of variance (ANOVA) using a one-factor model without replications were done for each trait and for each group of genotypes (CEAPOIU, 1968). Standard deviation:

Coefficient of variation (CV %):

II. Genotypic variability Seven early maturing maize synthetic populations derived from three different breeding programs were chosen for this study: 1) per se selection (Tu Syn 3 (per se) (1)), 2) recurrent selection (Tu Syn Mara, Tu Syn 1, Tu Syn 8), 3) recurrent reciprocal selection (Tu SRR 2I(5D) (1), Tu SRR 5D(2I) (1), Tu SRR 5DR (6I) (4)) were used in this study. These synthetic populations were well suited for the objectives of research as they had proven to be with high and low moisture content at normal harvesting time. They are genetically broad based populations improved for agronomic traits. These synthetic populations are under continuous genetic improvement for agronomic traits: grain yield capacity, early maturity, resistance to root and stalk lodging. Experimental designs. II-1-2) Seeds from the crosses (7 synthetic populations x 4 inbred lines-testers) were produced in a factorial mating design. Synthetics were crossed with four testers (inbred lines): two flint inbred lines (TD 233 and CO 255) and two dent inbred lines (TC 184 and TC 209). The test crosses and their parental forms were evaluated in four environmental conditions: two years 2009 and 2010 and two locations Turda and Targu-Mures respectively, for both per se and test cross performances. Complete block designs were used with 3 replications for per se and testcross trials respectively. Plant densities averaged 60 000 plants/ha in each experiment. Plots were 2-rows, 5m-long, with 0.7 m spacing between two rows. II) Statistical analysis of genotypic variation. Analysis of variance in testcross was performed for all traits within and among environments. Analysis of GARDNER and EBERHART 35 Research Journal of Agricultural Science, 44 (2), 2012 (1966) was used to partition genetic and environmental effects. Genotypes were considered as fixed effects while environments and replication (locations) within each environment were considered as random effects. The genotypes variance was decomposed orthogonal and non- orthogonal for: test cross hybrids, check hybrids and comparisons between the two groups. There were calculated values for the general combining ability (GCA) and specific combining ability (SCA) following the procedure describes by GRIFFING (1956) Model II, for factorial analysis: ĝm or ĝn = Xm . X.. (CABULEA, 1975) m m.n ĝm or ĝn = general combining effects of “m” and „n” parent n = synthetic populations - parental forms used as father m = inbred lines-tester used as mother

RESULTS AND DISCUSSIONS Description of per se variability. In all trials, coefficients of variability, both for local populations and for synthetics, were over 5% for most stags of vegetation period (table 1); they were higher for early vigour (15.1 to 15.3%) and stage of silking – physiological maturity (8.9% for local populations to 10.9% for synthetics). Although, there is little variation in the stage of sowing – physiological maturity (4.2% for synthetics to 4.4% for local populations) in the germplasm studied here. Table 1. Means values, range of variation, and coefficients of variation (CV) for stages of vegetation period in „TURDA” germplasm Stages of vegetation period: sowing – sowing – sowing – silking – Early Traits flowering silking physiological physiological vigor maturity maturity Germplasm ∑0 C Note Local Minimum 438.7 438.7 883.7 362.8 4 populations Mean 519.8 526.7 1012.2 485.5 6.8 Maximum 672.0 691.4 1172.1 600.9 9 (count = 208) Range 233.3 252.7 288.4 238.1 5 Variance 1382.2 1428.3 1996.6 1846.9 1.1 Standard Deviation 37.18 37.79 44.7 43.0 1.0 Standard Error 2.6 2.62 3.1 3.0 0.1 ConfidenceLevel 5.1 5.2 6.1 5.9 0.1 (95%) CV (%) 7.2 7.2 4.4 8.9 15.2 Turda Minimum 430.7 438.7 850.1 276.8 5 Synthetics Mean 536.9 549.1 1020.6 467.9 7.8 Maximum 619.4 664.9 1085.8 573.8 9 (count = 56) Range 188.7 226.2 235.7 235.7 4 Variance 1294.5 1536.0 1845.3 2619.8 1.4 Standard Deviation 36.0 39.2 43.0 51.2 1.2 Standard Error 4.8 5.2 5.7 6.8 0.2 Confidence Level 9.6 10.5 11.5 13.7 0.3 (95%) CV (%) 6.7 7.1 4.2 10.9 15.4  Coefficient variability (CV %)

In the same Table 1 it was also evident that local populations showed variability for maturity ranging between 233.3 ∑0 C in case of stages of sowing – flowering and 288.8 ∑0 C for stage of sowing – physiological maturity. The range of variation observed for synthetics was larger 36 Research Journal of Agricultural Science, 44 (2), 2012 than in local populations, ranging between 188.7 ∑0 C (sowing – silking) and 235.7∑0C (sowing – physiological maturity). Among local populations some interesting forms with earlier silking, most of them being collected from Maramures areas, were identified: Tulghes (438.7∑0C), Tarna Mare, Cerbal and Lancram (449.6 ∑0C), Corbu B189-84, Giulesti, Desesti, Lunca, Miercurea, Mara-1 and Ungheni 1 (460.1∑0C). In the studied germplasm were local populations which have been noted by longer period between sowing-silking and shorter maturity between silking - physiological maturity: Rosu de Beriu, Eremitu, Campeni, Mara 2, Stanceni (table 2).

Table 2 Per se values of some stages of vegetation period of local populations, as maize maturity rating equivalents I. Local populations noted by shorter period II. Local populations noted by shorter period between sowing-silking between silking - physiological maturity Stages of vegetation period: Stages of vegetation period: sowing – silking – sowing – silking – Local sowing – sowing – Local sowing – sowing – No. physiological physiological No. physiological physiological populations flowering silking populations flowering silking maturity maturity maturity maturity ∑0 C ∑0 C 1 Atid 460.1 500.7 110.2 509.5 1 Apoldu de Sus 500.7 512 930.2 418.2 2 Aschileul Mare 460.1 500.7 110.2 509.5 2 Rosu de Beriu 587.1 587.1 949.9 362.8 3 Bereni 460.1 470.5 914.9 444.4 3 Berind(CN3-84) 538.9 573.3 982.7 409.4 4 Borsa 460.1 500.7 110.2 4 Cisteiul de 531.1 547.4 970.2 509.5 Mures 422.8 5 Corbu B189-84 460.1 460.1 940.5 480.4 5 Campeni 531.1 547.4 949.9 402.5 6 Cerbal 449.6 449.6 914.9 465.3 6 Eremitu 500.7 500.7 899.3 398.6 7 Cerbal Aries 449.6 449.6 930.2 480.6 7 Erina 522.3 538.9 949.9 411 8 Desesti 449.6 460.1 917.9 457.8 8 Mihaiesti CN 42 522.3 522.3 949.9 427.6 9 Desesti 2 460.1 470.5 899.3 428.8 9 Mara 2 481.6 531.1 940.5 409.4 10 Giulesti 460.1 460.1 1061 600.9 10 Rosu de Suatu 538.9 538.9 949.9 411 11 Hateg 460.1 460.1 132.3 572.2 11 Seini 522.3 538.9 949.9 411 12 Lunca 449.6 460.1 982.7 522.6 12 Stanceni 609.7 609.7 1010.2 400.5 13 Lancram 449.6 449.6 124.3 574.7 13 Selimbar 619.4 619.4 1042 422.6 14 Miercurea 460.1 460.1 110.2 550.1 14 Sinca Noua 599.4 629.4 1042 412.6 15 Mara 1 449.6 460.1 949.9 Mean/208 489.8 populations 519.7 526.6 1012.0 485.4 16 Pascani 460.1 460.1 995.8 535.7 17 Tulghes B160- 449.6 438.7 124.3 84 585.6 18 Tulghes B179- 438.7 438.7 970.2 84 531.5 19 Zetea(B 147-84) 449.6 449.6 982.7 533.1 20 Zetea(B145-84) 449.6 449.6 982.7 533.1 Mean/208 populations 519.7 526.6 1012.0 485.4

II. The genetic value of the synthetic populations II.1. Per se values of some stages of vegetation period of parental forms – synthetic populations, as maize maturity rating equivalents The synthetic populations used as parental forms Tu Syn Mara and Tu SRR 5DR (6I) (4) were chosen for this study mainly because of the large difference in maturity between them. This difference in maturity is reflected in the comparative sum of the degrees of temperature (∑0 C) which were for the period from sowing to silk emergence 526.5 → 627.4 ∑0 C, sowing to pollen shedding 509.3→588.0 ∑0 C and sowing to physiological maturity 1091.0 → 1158.6 ∑0 C respectively (table 3). The difference in sum of the degrees of temperature (∑0 C) to silking was 100.90 C and 67.60 C for physiological maturity respectively. The difference in maturity between the parents is therefore very similar when measured by these two characters. The data from the parents also indicated that, on the average, silking occurred later (+38.50 C) than pollen shedding. The difference in percentage of grain dry matter at harvest between the parental forms indicated that the high values for dry matter content in grain at harvest were obtained 37 Research Journal of Agricultural Science, 44 (2), 2012 from synthetic populations Tu Syn Mara, Tu SRR 5D (2I) (1), Tu Syn 1, Tu SRR 2I (5D) (1). Lowest values for the percentage of dry matter were obtained from synthetics Tu Syn 3 (per se) (1) (very significant lower than the average synthetic) comparable to those recorded for some of the check hybrids (table 3). Therefore, Tu Syn Mara is the most early of the parent forms. Table 3. Per se values of some stages of vegetation period of parental forms – synthetic populations, as maize maturity rating equivalents Stages of vegetation period:

sowing – sowing- sowing – silking – Early Grain dry flowering silking physiologi- physiologi- vigor Traits Genotype matter at No. cal cal harvest maturity maturity % ∑0 C Note 1. Tu Syn Mara 82.2 509.3 526.5 1091.0 564.5 6 2. Tu Syn 1 80.7 510.5 569.6 1134.8 565.2 6-7 3. Tu Syn 8 80.1 557.5 598.9 1106.1 507.2 6 4. Tu SRR 2I(5D) (1) 80.1 540.7 575.3 1107.1 531.2 6-7 5. Tu SRR 5D (2I) (1) 80.8 555.6 587.0 1131.5 544.5 6 6. Tu Syn 3 (per se) (1) 77.9 563.6 627.4 1158.6 531.2 6-7 7. Tu SRR 5DR (6I) (4) 78.8 588.0 610.3 1128.0 518.0 5-6 Mean of check hybrids 78.0 - - - - - Mean 80.1 546.5 585.0 1122.4 537.5 -

II. 2. Genetic values of the seven synthetic populations for maturity The determination of the genetic value of those seven synthetic consisted in their crossing with four testers (inbred lines): two flint inbred lines (TD 233 and CO 255) and two dent inbred lines (TC 184 and TC 209). The test crosses and their parental forms were evaluated in four environmental conditions: two years 2009 and 2010 and two locations Turda and Targu- Mures respectively, for both per se and test cross performances. Testcross hybrids were compared with four commercial hybrids: Turda Mold 188, Turda 165, Turda SU 181 and Turda 201. The expression of grain dry matter content was significantly (P< 0.05) different for all crosses in each environment (table 4). The interaction term of environment x genotype was significant. Table 4. Analysis of variance of the grain dry matter content of testcross hybrids “tester x synthetic population” (2 experimental years, 2 locations) compared with the check (commercial) hybrids Source of variation df Mean squares F test Significance Years (Y) 1 2500,02 1366,13 ** Locations (L) 1 59,38 32,43 ** (L x Y) 1 3,42 1,88 31 39,21 Genotypes (G) 21,46 ** 31 7,74 (G x Y) 4,24 ** 31 3,07 (G x L) 1,68 * (G x Lx Y) 31 3,95 2,17 ** 1,83 Error 248 An analysis of variance on the plot means indicated significant differences between years, locations and between genotypes. The error mean squares were low, indicating the existence of good experimental conditions. The hybrids realized with Tu Syn Mara, Tu SRR 5 D (2I) (1) and Tu Syn 1 were with 38 Research Journal of Agricultural Science, 44 (2), 2012 the highest dry-matter content (81.3%, 80.1% and 79.9% compared to average of check hybrids); the difference in the first situation is very significant statistically (table 5). Table 5 General combining ability for kernels dry matter content (%) of the synthetic populations (ĝn) and tester inbred lines (ĝm) TC 184 Mean - Tester - inbreds TC 209 CO 255 TD 233 cmsC synthetics ĝ Synthetics n % Tu Syn Mara 80.74 81.50 82.93 79.97 81.29 1.80 Tu Syn 1 78.96 79.52 81.42 79.85 79.94 0.45 Tu Syn 8 78.72 78.43 81.82 77.15 79.03 -0.46 Tu SRR 2I(5D) (1) 77.85 78.40 80.70 78.37 78.83 -0.66 Tu SRR 5D(2I) (1) 80.28 80.08 82.75 77.33 80.11 0.62 Tu Syn 3 (per se) (1) 77.83 77.64 80.22 75.09 77.69 -1.79 Tu SRR 5DR (6I) (4) 78.90 79.64 81.49 78.10 79.53 0.04 Mean - tester 79.04 79.32 81.62 77.98 79.49

ĝm -0.45 -0.17 2.13 -1.51 LSD (0.05) comparisons genotypes = 1, 09 %

The highest values of additive effects for grain dry matter content were recorded at: Tu Syn Mara (ĝn = +1,80), Tu SRR 5D (2I)(1) (ĝn = +0,62) and Tu Syn 1 (ĝn = +0,45). Therefore, Tu Syn Mara, Tu SRR 5D (2I)(1) and Tu Syn 1 produced hybrids with the most early maturity. The most late hybrids were those produced by the synthetic populations Tu Syn 3(per se) (1) (ĝn = -1,79), Tu SRR 5D (2I)(1) (ĝn =-0,66) and Tu Syn 8 (ĝn = - 0,46) (table 5). Table 6. Specific combining ability effects (ŝij) for kernels dry matter content of the synthetic populations and tester inbred lines Genotype TC 184 cmsC TC 209 CO 255 TD 233 Tu Syn Mara -0.10 0.39 -0.49 0.19 Tu Syn 1 -0.53 -0.24 -0.65 1.42 Tu Syn 8 0.14 -0.43 0.66 -0.37 Tu SRR 2I(5D) (1) -0.54 -0.25 -0.26 1.05 Tu SRR 5D(2I) (1) 0.62 0.14 0.51 -1.27 Tu Syn 3 (per se) (1) 0.58 0.12 0.40 -1.10 Tu SRR 5DR (6I) (4) -0.18 0.28 -0.18 0.08 LSD (0.05) comparisons genotypes = 1,09 % Generally, absolute values for non-additive effects were lower than the absolute values of the highest additive effects (ĝm and ĝn). SCA was positive for: - TD 233 x Tu Syn 1 - ŝm x n = +1, 42; - TD 233 x Tu Syn 2I (5D)(1) - ŝm x n = +1,05; - CO 255 x Tu Syn 8 - ŝm x n = +0,66; - TC 184 cms C x Tu SRR 5D (2I)(1) - ŝm x n = +0,62.

CONCLUSIONS 1. The local populations and synthetics studied may be used as sources of initial material for precocity in maize breeding programmes. 2. There is variability between genotypes for maturity; coefficients of variability were over 5% for most stages of vegetation period. 3. Most of the local populations with a short vegetation period were collected in the area of Maramures. 4. The synthetic populations studied for their genetic values in heritabity of precocity were well suited for the objectives of research. 39 Research Journal of Agricultural Science, 44 (2), 2012 5. The highest values of additive effects for grain dry matter content were recorded at: Tu Syn Mara (ĝn = +1, 80), Tu SRR 5D (2I) (1) (ĝn = +0, 62) and Tu Syn 1 (ĝn = +0, 45). 6. Tu Syn Mara, Tu SRR 5D (2I) (1) and Tu Syn 1 produced hybrids with the most early maturity. 7. Nonaditive gene effects have brought the contribution in the determinism of dry matter content in grain at normal harvesting time, but their role was, however, lower within framework of this experimental system, in comparison with the additive effects. 8. The process of improvement of synthetic population may continue as there is still enough genetic variability. 9. All local populations (landraces) and synthetics are currently used in the framework of breeding and genetic program at the Agricultural Research Station, Turda – Romania (ARS Turda).

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